/*
 * Copyright (c) 2011-2014 Pivotal Software, Inc.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.camunda.bpm.extension.reactor.projectreactor.support;

/**
 * Assertion utility class that assists in validating arguments. Useful for identifying programmer errors early and
 * clearly at runtime.
 * <p/>
 * <p>For example, if the contract of a public method states it does not allow {@code null} arguments, Assert can be
 * used to validate that contract. Doing this clearly indicates a contract violation when it occurs and protects the
 * class's invariants.
 * <p/>
 * <p>Typically used to validate method arguments rather than configuration properties, to check for cases that are
 * usually programmer errors rather than configuration errors. In contrast to config initialization code, there is
 * usally no point in falling back to defaults in such methods.
 * <p/>
 * <p>This class is similar to JUnit's assertion library. If an argument value is deemed invalid, an {@link
 * IllegalArgumentException} is thrown (typically). For example:
 * <p/>
 * <pre class="code"> Assert.notNull(clazz, "The class must not be null"); Assert.isTrue(i > 0, "The value must be
 * greater than zero");</pre>
 * <p/>
 * Mainly for internal use within the framework; consider Jakarta's Commons Lang >= 2.0 for a more comprehensive suite
 * of assertion utilities.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @author Colin Sampaleanu
 * @author Rob Harrop
 * @since 1.1.2
 */
@SuppressWarnings({"rawtypes"})
public abstract class Assert {

  /**
   * Assert a boolean expression, throwing {@code IllegalArgumentException} if the test result is {@code false}. <pre
   * class="code">Assert.isTrue(i &gt; 0, "The value must be greater than zero");</pre>
   *
   * @param expression a boolean expression
   * @param message    the exception message to use if the assertion fails
   * @throws IllegalArgumentException if expression is {@code false}
   */
  public static void isTrue(boolean expression, String message) {
    if (!expression) {
      throw new IllegalArgumentException(message);
    }
  }

  /**
   * Assert that an object is {@code null} . <pre class="code">Assert.isNull(value, "The value must be null");</pre>
   *
   * @param object  the object to check
   * @param message the exception message to use if the assertion fails
   * @throws IllegalArgumentException if the object is not {@code null}
   */
  public static void isNull(Object object, String message) {
    if (object != null) {
      throw new IllegalArgumentException(message);
    }
  }

  /**
   * Assert a boolean expression, throwing {@code IllegalStateException} if the test result is {@code false}. Call isTrue
   * if you wish to throw IllegalArgumentException on an assertion failure. <pre class="code">Assert.state(id == null,
   * "The id property must not already be initialized");</pre>
   *
   * @param expression a boolean expression
   * @param message    the exception message to use if the assertion fails
   * @throws IllegalStateException if expression is {@code false}
   */
  public static void state(boolean expression, String message) {
    if (!expression) {
      throw new IllegalStateException(message);
    }
  }

  /**
   * Assert a boolean expression, throwing {@link IllegalStateException} if the test result is {@code false}. <p>Call
   * #isTrue(boolean, String) if you wish to throw {@link IllegalArgumentException} on an assertion failure. <pre
   * class="code">Assert.state(id == null);</pre>
   *
   * @param expression a boolean expression
   * @throws IllegalStateException if the supplied expression is {@code false}
   */
  public static void state(boolean expression) {
    state(expression, "[Assertion failed] - this state invariant must be true");
  }

}
